Ill back it also, I've got a custom size one from thekiinnng in Canada as I've set magnets in my cast aluminium bed. Works great but the issue I've faced already with the textured sheet was the pores went through to the steel sheet in some places and began to rust underneath the pei resulting in it lifting off within 2 months .
I hope you can achieve a reliable quality

The size limit is stated on the Kickstarter. We also have a FAQ section over there as to the current limitations. The future is bright however for making any size if the Kickstarter is successfully funded.